Scary Terry makes Halloween and haunted house props. This one is called Skelevision.

The guest would enter a hallway and see themselves in a mirror at the end of the hall. All of a sudden, the lights would go out, spooky sound effects would play and then a skeleton would appear where they previously saw themselves in the mirror. The skeleton would be frantically waving its arms. After a few seconds, the skeleton would disappear and the guest would once again see themselves in the mirror.